First, the difference between the ARX and kite you tried, is ARX is a 2001 kite!!! NOT 2002, so it is 2 generations ahead. If you compare the 2002 kites - Wipika, Naish (X2), North Rhino, Takoon, etc, and the newer 2003 kites, the difference will be less drastic, but still noticable - as from 2002 to 2003, the main imporvements are to saftey systems, and general workmanship of the kite quality - with a few improvements to the flying capabilities. The two most noticable attributes in the 2003 kites, are their speed, and stability - They are all very fast, and very stable....
Take for example the Bronco, from Ocean Rodeo, which I am riding a lot these days. It has the smallest bar of any kite, but is just as fast as the fastest kites - and it is super stable in the air.... A pleasure to fly.
Same with the Caution kites. I flew the 15m, and was very pleased by its speed, which was very fast...
In my opinion 2003 kites are all on such a similar level that it is really the riders skill that will make the difference to the way they perform.
Have fun... ciao